1. Field
This invention relates to methods and apparatus for separating suspended settleable and flotable substances (and immiscible liquids) from carrier liquids. More particularly, this invention is directed to improved apparatus of the gravity separation type.
2. State of the Art
U.S. Pat. No. 3,951,818 discloses apparatus of the type known as a "chevron clarifier" because of the characteristic configuration of its interior components. The chevron clarifier operates on the gravity separation principle. A plurality of separation elements (each comprising a stacked array of individual settling compartments) are suspended within a tank in approximately vertical parallel arrangement. The separation elements are paired to form a collection channel between each such pair. Each settling compartment is formed by spaced plates which are connected by an approximately vertical back plate to form an apex disposed approximately horizontally across the tank. The apex includes a predetermined number of calibrated separation apertures through the back plates. These apertures serve to evenly distribute the flow across the apex and to regulate the amount of liquid passing from the individual compartments into the collection channel. This arrangement, although simple and effective, has certain disadvantages.
The separation efficiency of the chevron clarifier is low when it is applied to the handling of material having a low concentration of suspended solids. In some instances, the feed mixture, or suspension, is unevenly distributed in the vertical direction as it enters the separation elements, thereby causing local overloading and decreased throughput.
The space requirements of the prior art chevron clarifiers are influenced adversely by the existence of the large vertical collecting channels extending between the paired separation elements.
The settling compartments used heretofore have been open at each side to the tank interior. This construction has permitted a surprising amount of short circuiting, resulting in decreased separation efficiencies, especially in the processing of low solids suspensions. Moreover, shortcircuiting imposes a practical upper limit on the concentration level obtainable.
Prior art chevron clarifiers constructed for a particular application cannot ordinarily be used for another application involving different settling and other characteristics. The separation apertures have not been readily accessible for cleaning and maintenance, making it necessary to take the clarifier out of service for such operations.
There remains a need for an improved apparatus which can perform the functions of a chevron clarifier while avoiding the problems of the prior art.
In addition to the chevron clarifier described, other pertinent prior art includes U.S. Pat. Nos. 349,990; 653,012; 1,190,863; 2,000,606; 2,314,977; 3,718,257; 3,727,770; and 4,056,477; all of which disclose various clarifier and/or thickener devices and methods. The "PURI-STAT" clarifier/thickener, a chevron-type device, is described in an undated brochure published by Puri-Stat Incorporated, 720 South Colorado Boulevard, Denver, Colo., 80222. The Graver Floc Barrier is described in Bulletin WC-146 published by Graver Water Conditioning Co., U.S. Highway 22, Union, N.J., 07083. Various gravity settler/thickener systems based upon the Lamella principle are described in Bulletin LT-103 published by Parkson Corporation, 5601 N.E. 14th Avenue, Fort Lauderdale, Fla., 33307.